But to answer unterhausen, I chose to put each course segment (TCX file) on a separate SD card. Redundancy. I've also had trouble with the device giving odd directions when I had more than one route on a card. It's possible that was an error on my part, but I've heard that complaint from other riders as well. The Euro map I used on that tour was about 4 GB. I used 8 GB cards. Garmin FAQ used to say that larger cards slowed the device, but that FAQ no longer has that statement. Cards up to 32GB can be used.